The difficulty levels provided in Halo 2 are the same as Halo 1. The Legendary setting is the most difficult, the enemies are the strongest and most aggressive. In Halo 1 most players used the co-op mode to leapfrog throught the levels. Bungie has fixed this in Halo 2. Meaning that if one player dies in legendary then the checkpoint must be restarted. This makes legendary very difficult, however, we will list some good tips for getting through it:

Use grenades as much as possible. The enemy shields are very strong and takes more than a full clip of most guns to take down.

The Energy Sword is no longer a one-hit-kill it can take several strikes to kill an enemy.

Move slowly and try to stay behind cover as much as possible.

Gun turrets can be very useful, but remember you are a sitting duck if you stay too long.

Use vehicles as much as you can but the enemies will try to steal them.

Enemies work together, try to break them apart into smaller groups as best you can.